Method and apparatus for neutron detection utilizing pulse height discrimination and pulse shape discrimination

Abstract

Embodiments relate to an advanced fast and thermal neutron detector material composition with the properties useful for Special Nuclear Material (SNM) detection. Specific embodiments of the material composition result in two excimer scintillation light production mechanisms that provide two corresponding independent techniques for gamma discrimination; namely Pulse Shape Discrimination and Pulse Height Discrimination. A dual discrimination method, Pulse Shape and Pulse Height Discrimination (PSHD), can be implemented relying on both pulse height discrimination and pulse shape discrimination, and can allow the operation of large area, fast and thermal neutron detectors.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit of U.S. Provisional Application Ser. Nos. 61 / 714,588, filed Oct. 16, 2012, 61 / 755,661, filed Jan. 23, 2013, and 61 / 768,495, filed Feb. 24, 2013, the disclosures of which are hereby incorporated by reference in their entirety, including all figures, tables and amino acid or nucleic acid sequences.BACKGROUND OF INVENTION[0002]Embodiments of the subject invention pertain to detection of radiation related to, for example, nuclear nonproliferation activities. The Office of Nuclear Nonproliferation Research and Development has been focused on enabling the development of next generation technical capabilities for radiation detection of nuclear materials. Recently, the Special Nuclear Material (SNM) Movement Detection Program created an evolving technology roadmap that identified the following fundamental objectives:[0003]1. detect shielded highly enriched Uranium;[0004]2. detect SNM at standoff distances; and[...

AI Technical Summary

Benefits of technology

The patent describes the use of plastics containing covalently bonded boron compounds to create effective thermal neutron detectors with high gamma discrimination. By using specific polymers that can dissolve polar compounds, the plastic can be made into a high-spatial resolution detector with good thermal neutron capture and fast neutron detection. The plastic scintillator can also offer good gamma discrimination. The patent also describes the use of a liquid solvent scintillation matrix for thermal neutron detection, which can provide self-assembled dimers and effective gamma discrimination. The use of highly polar liquids can achieve high concentrations of lithium compounds, and relatively short mean free paths for thermal neutrons can be obtained. The detection system can also have improved safety features due to the formation of a solid gel.

Problems solved by technology

There are many methods under investigation, yet none have appeared to come very close to meeting the challenging requirements.

In large area detectors, it is almost inevitable that loss of some scintillation light will result in a reduced gamma discrimination factor.

Accordingly, it appears the gamma ray discrimination of these detectors is inadequate for effective detection of SNM.

In general, the PSD method suffers from an inherent disadvantage; the pulse shape discrimination is effective only after a time delay, at which point the pulse height has fallen by at least an order of magnitude.

As a result, there is a major loss of quantum statistical information when using PSD, which limits the ability to provide powerful gamma ray discrimination in large detectors.

This implies the TOF method would likely offer no improvement in the gross neutron counting sensitivity beyond that of existing RPMs.

In addition, the intrinsic detection efficiency of up to 4% is inadequate to perform fast neutron multiplicity measurements, which are powerful indicators of SNM material.

However, lithium forms polar compounds that are very poorly soluable (about (0.01% wt / wt) in non-polar scintillating plastics, such as polystyrene (PS) and polyvinyltoluene (PVT).

Accordingly, a highly efficient, thermal neutron plastic scintillation detector has not yet been achieved.

Therefore, despite major efforts by Federal Agencies, National Laboratories and many researchers, there has been less progress than desired in meeting the fundamental objectives of improved neutron detection for the SNM Movement Detection Program.

Images